1. Technical Field
This application is related to the field of chirped-pulse amplifier systems.
2. Related Technology
Chirped-pulse amplification (CPA) laser systems were initially developed in the 1980s. Before CPA systems were developed, laser amplifiers generating ultrashort pulses were limited in optical intensity by a tendency of high optical power pulses to cause nonlinear pulse distortion or to damage the amplifier gain medium or the optical elements. In CPA laser systems, the pulses are chirped and temporally stretched to a much longer duration before passing through the gain medium, so the peak power is kept at a lower level during amplification. A dispersive compressor then removes the chirp and temporally compresses the pulses to a duration similar to the input pulse duration. CPA laser technology has been widely adopted for high power lasers, compact high power lasers (e.g., table top terawatt (T3) lasers) and in applications such as laser wakefield accelerated electron beam systems.    H. Kiriyama et al., Opt. Lett. 37, 3363, (2012) and K. B. Wharton et al., Phys. Rev. E 64, 025401, (2001) discuss laser pulse contrast and shape for subpicosecond, multiterawatt chirped-pulse amplification (CPA) laser systems.    K. B. Wharton et al., Phys. Rev. E, Vol. 64, pp. 025401-1-025401-4 (R), July 2001, discusses the effects of non-ionizing prepulses in high-intensity laser-solid interactions. Both W. P. Leemans et al., Phys. Rev. Lett. 89, 174802, (2002) and S. P. D. Mangles et al., Plasma Phys. Cont. Fusion 48, B83, (2006) discuss pulse shape and pre-pulse contrast in terms of the usability of laser wakefield accelerated electron beams.    H. Kiriyama et al., Opt. Lett. 37, 3363, (2012), M. P. Kalashnikov et al., Opt. Lett. 30, 923 (2005), A. Jullien et al., Opt. Lett. 30, 920 (2005), and K.-H. Hong et al., Appl. Phys. B 81, 447 (2005) disclose techniques for reducing amplified spontaneous emission (ASE) that can manifest as nanosecond-scale pedestal superimposed on the main pulse.    A. Verhoef, J. Seres, K. Schmid, Y. Nomura, G. Tempea, L. Veisz, and F. Krausz, Appl. Phys. B, Vol. 82, 513, (2006) discusses compression techniques for a 5 femtoseconds 0.2 terawatt Ti:sapphire CPA laser system.    M. P. Kalashnikov and K. Osvay, Proc. SPIE 5975, 59750E (2006) and C. Hooker et al., Opt. Express 19, 2193 (2011) discuss recent efforts in contrast enhancement related to prepulses and pedestals in the several picosecond to a few nanosecond range.    A. Jullien et al., Opt. Lett. 30, 920 (2005) and C. Hooker et al., Opt. Express 19, 2193 (2011) describes picosecond scale pedestals of 10−5-10−4 for CPA laser systems. C. Hooker et al., Opt. Express 19, 2193 (2011) demonstrated that scatter from the diffraction gratings in the pulse stretcher contribute to a short time scale (20 ps) pedestal around the main pulse.